There have been quite a few cases of foreign NATO pilots receiving inadequate briefings in the UK, as well. Consequently, their understanding of the rules and procedures is also inadequate, and their performance similarly below par. It's not just RAF pilots misbehaving in the skies above Tromsų.
In this case, however, RAF pilots were in UK airspace which, presumably, they knew well, and knew the possibility of helos operating between the rigs and the mainland.
Furthermore, one assumes that the ATCO could see the relative speed of the aircraft on his screen, yet failed to alert the Jaguar mates to the likely traffic type.
I echo the comments above. This was, as far as I can see, a case of complacency, lack of attention to detail and lack of professionalism.